Electro-pneumatic transducer



Oct. 17, 1961 Filed June 2. 1959 J. W. ROBINS ETAL ELECTRO-PNEUMATIC TRANSDUCER 2 Sheets-Sheet 1 JOHN W. ROBINS OSCAR J". HARDEGEN IN VENTORS WZw Oct. 17, 1961 J. w. ROBINS ETAL ELECTROPNEUMATIC TRANSDUCER 2 Sheets-Sheet 2 Filed June 2, 1959 JOHN W ROBINS OSCAR J. HARDEGEN INVENTORS Patented Oct. 17., 1961 3,004,546 ELECTRO-PNE'UM'ATIC TRANSDUCER John W. Robin's, Westwood, and Oscar J. Hardegen, feymouth, Mass, assignors to Worthington Corporation, Harrison, NJ., a corporation of Delaware Filed June 2, 1959, Ser. No. 817,608 Claims. (Cl. 13782) This invention relates to a device for transducing an electrical signal into a pneumatic signal and more par- 2 substantially hollow rectangular casing 1 having a cover 2 and provided with bosses as at 3a, 3b, 3c, 3d, 3e and 3;.

- Bosses 3a,- 3b, 3c and 3d receive the upper pole piece 4 ticularly to a force-balance electro-pneumatic device which provides an. accurate means of converting a low power D.C. electrical signal into a proportional pneumatic output signal. i

The control of processes and systems from panel boards at points remote from the process or system or the transmission of signals from one point in a process to another point in the process remote from the signal presents many problems. I

s The transmission of these signals through electrical current conducting lines presents a relatively simple Way of passing the signal substantially instantaneously to some remote point. However, the present type controls, actuators or relays now utilized are primarily pneumatically or hydraulically actuated and accordingly it is necessary to develop a device which can convert these electrical signals to proportional pneumatic or hydraulic signals for operating rthese actuators.

The present invention covers an electro-pneumatic transducer of the force-balance type wherein a coil suspended in a strong magnetic field receives an electrical signal and converts this signal into a force exerted on a pivoted beam having an associate bathe thereon coacting with a pneumatic nozzle wherebyva'rying back pressure is produced in a pneumatic system and is transmitted by the output line in the system to a point of use, the transducer being characterized by a freely. floating ball to control the nozzle orifice which eliminates critical alignment problems, and a means for calibrating and adjusting the magnetic field to permit the coil to operate through its entire range.

Accordingly, it is an object of thepresent invention to I provide an electro-pneumatic transducer having a balanced beam arrangement which is adapted to convert elec-. trical signals from any desired source into changes in fluid pressure for use in operating fluid pressure actuated operators.

It is an object of the present invention to provide an electro-pneumatic transducer having relatively simple means to adjust for full input signal range.

It is another object of the present invention to provide an electro-pneumatic transducer with a floating ball type nozzle and bafiie arrangement which eliminates problems of critical alignments of the baffle relative the nozzle.

Further objects and advantages of the invention will become evident from the following description withreference to the accompanying drawings, inwhich:

FIGURE 1 is a plan view of the invention with the cover removed. I

FIGURE 2 is a view taken on line 2-2 ofFIGURE 1.

FIGURE 3 is a plan view with the cover removed and s the force beam balance removed.

FIGURE 4 is an enlarged view of the nozzle bafiie arrangement showing a manifold arrangement for the pneumatic system. I 7

FIGURE 5 is a partial section showing the flexurebear ing connections. p v s FIGURE 6 is a front viewof the flexure bearing connections. l

FIGURE 7 is a view of a modified form of the invention wherein a relay is included in the pneumatic system.

Referring tothe drawings, FIGURES 1 and 2 show a of the magnetic sub-assembly generally designated A in FIGURE 2 of the drawings. Bosses 3e and 37" provide means for mounting the terminal board sub-assembly generally designated B, also shown in FIGURE 2. The upper polepiece 4 is connected to the bosses 3a, 3b, 3c and 3d by means of threaded members 5, and as shown in FIGURE 3 the upper pole piece has an opening 6 formed therein. g

In the magneticv sub-assembly A a lower pole piece 7 coacts with the upper pole piece 4. The lower pole piece 7 includes acylindrical body portion 8 having an annular lip 9 at the upper end and a flange 10 about the lower end. An annular magnet 11 is connected between the lower face of the upper pole piece 4 and the upper, face of the flange 10 by any suitable means such as an epoxy resin so that the annular lip 9 of the lower pole piece is disposed in the opening 6 of the upper pole piece and forms therewith an annular space generally designated 12.

A coil bobbin 13 having a downwardly depending annular portion 14 to. mount a coil 14aof current conducting material is disposed so that in assembled position the depending annular portion 14 with its coil 14a fits into the annular space -12 formed between the lip 9 and the opening 6.

The coil bobbin 13 is connected to a channel type beam 15 by threaded members 16 which beam in turn is pivotably connected, by horizontal bearing elements 17 and vertical flexure bearing elements 18 spaced on. opposite sides of the, centerline of the beam, to the upper pole piece as hereinafter described. When the coil 14a and the coil bobbin 13 are moved the beam which is fixedly connected thereto will also pivot about the flexure hearingelements.

The coil 14:: will be moved responsive to electrical signals delivered thereto. Thus FIGURES l and 2 show electrical connecting lines 19 and 20 connected at one end to the coil 14a and at the other end to detachable connectors21 and 22 on the terminal board B. The detachable connectors in turn connect by lines 23 and 24 to terminals 25 and 26. which terminals in turn communicate with the input signal lines27 and 28 connected to any desired source of signals not shown.

Calibration adjustment means Because the coils are wound they are not uniform and it is necessary to provide means to calibrate the transducer so that it will transduce a pneumatic signal over the full input range. I a

This is accomplishedby a bore 30 formed in thecenter of the soft, ironlower pole piece into which is threaded a span adjuster 31. r

The bore 30 and the span adjuster 31 are shaped at their respective inner ends so that the span adjuster can be brought into snug engagement with the inner wall of the bore 30. By moving the span adjuster outwardly firom the innerwall of the bore 30 a gap is formed therebetween and this gap provides means for, changing the reluctance of the lower pole piece relative the upper pole piece and hence the. gap flux'therebetween for the desired calibration adjustment.

A span adjusterlocking screw 32 is provided to lock the span adjuster in the desired calibrated position and a casing plug 33 seals the opening 34 in the casing 1 through which any. suitable. instrument may be inserted to engage the slot 35 on the span adjuster.

Beam mounting v The illustrated device is or the fierce-balance type. In this arrangement the force generated by the electromagnetic means is directly reflected by a proportional deflection of the beam. The beam in turn coacts with a nozzle and is balanced by the pneumatic force exerted at the nozzle.

FIGURES 2, 3, 5 and 6 show that the beam is mounted by means of the horizontal flexure bearing elements 17 and the vertical flexure bearing elements 18, two pairs of these elements being provided-one on either side of the centerline of the transducer.

A transverse bearing block 40 on the beam and the adjacent end and face of the upper pole piece 4 provide means for mounting these respective flexure bearings. The horizontal flexure bearing elements are connected at one end as by threaded means 41 to the underside of the bearing block 40 and the upper face of the upper pole piece by threaded means 42. Similarly, the vertical flexure bearing elements 18 are connected on the side face of the bearing block by threaded members 43 at one end and at the other end to the side face of the upper pole piece 4 by threaded members 44.

The flexure bearing elements as shown in FIGURES 5 and 6 are provided with arcuate cut-outs 45 in the medial portions to permit the flexure bearings to be aligned and for closer spacing relative each other. The bearing block 40 and the upper pole piece 4 will be beveled as at 46 and 47 to provide substantially frictionless movement oi the beam on movement of the coil 14a and coil bobbin 13 during the operation of the present device.

In order to balance the beam a beam balance weight 48 is attached to the end of the beam. In addition, to insure accurate positioning of the beam in assembled position a zero adjusting means generally designated 49 is also shown. This type zero adjusting means is well known in the art and hence not more fully described.

Nozzle arrangement The beam 15 coacts with a nozzle generally designated N which is the by-pass means for regulating the pressure of the fluid delivered from the device to the actuator or operator depending upon the specific arrangement.

Thus, FIGURES 2 and 4 show that the casing is provided with a pressure fluid chamber 50. The pressure fluid chamber 50 has an inlet 51 in communication with a flame arrestor chamber 52 formed in the connector 53 threadedly mounted in the casing 1. A flame arrestor 54 in the flame arrestor chamber provides means to prevent explosions in the pneumatic circuit.

The connector has a nipple 55 which provides means for detachably connecting the manifold member 56 to the transducer.

A communicating passage 57 in the nipple 55 connects with the main passage 58 in the manifold so' that pressure fluid delivered through the inlet line 59 will freely pass through the main passage 58, communicating passage 57, flame arrestor chamber 52 and inlet 51 into the chamber 50 in the casing.

The pressure of the fluid delivered to the chamber 50 is adjusted down to the desired limit by a suitable type of pressure regulating means generally designated 60, such as a fixed on'fice type, as is well known in the art.

The fluid from the main passage 58in the manifold discharges through an outlet line 61 'at a pressure which is a function of the coaction between the beam 15, the nozzle assembly N and the fixed orifice 60.

The nozzle assembly N shown clearly in FIGURE 4 of the drawings includes an annular member 62 threadably mounted in a threaded opening 63 which communicates with the chamber 50. V

- The nozzle has a passage 64 which communicates at its inner end with the chamber 50 and opens to atmosphere at the end remote from the chamber end.

At the end of the annular member 62 remote from the chamber end the passage is counterbored as at 65 and freely disposed in the counterbored section is a ball member 66 which is restrained from escaping from the counterbore by the baflle 67 fixedly connected to the end of the beam 15, all of which is clearly shown in FIG URE 4 of the drawings.

The counterbore 65 communicates with transverse slots as at 65a to permit pressure air to escape from passage 64. Those skilled in the art know that the size of passage 64 is relatively greater than the size of the fixed orifice 60. For example, the fixed orifice 60 may have a diameter of approximately 14 l0 while that of the passage 64 will be l0 Thus, it will require a relatively small movement of the ball relative the end of the passage 64 at its point of communication with the counterbore to regulate the flow area through the ball cage provided by the counterbore.

It will be understood, however, that while a ball cage is shown in the preferred form of the invention that the ball could operate without the cage by reason of the slight movements required to adjust the flow area through passage 64. The ball cage provided by the counterbore 65 is preferred because it eliminates the adverse eflects that might be introduced by lateral movement of the ball relative the outlet of passage 64 as would be the case with out a ball cage; the ball in assembled position in the ball cage has only limited space to move laterally the clearance between the ball and the cage being in the order of 2 X 10*.

This arrangement provides a self-centering, self-aligning nozzle assembly and overcomes one of the critical alignment factors between baffle and nozzle which has existed heretofore.

Operation The device can be operated as a direct action or a reverse action mechanism.

With direct action, an increase in the electrical signal increases the output pressure of the pressure fluid. On increase in the electrical signal from the signal source to the coil the coil bobbin 13 and hence the beam and baflle connected thereto are moved downwardly. This in turn produces a downward force on the ball floating member 66 on the pressure air escaping through the passage 64 and produces nozzle back pressure. The back pressure will increase until the force exerted by the back pressure on the ball and baffle equals that exerted by the coil 14a. This back pressure is reflected uniformly through the pressure fluid in the chamber 50, the communicating inlet 51, the flash arrestor chamber '52, communicating passage 57 and main passage 58 to produce an output pressure in the outlet line 61 proportional to the electrical signal.

Reverse action wherein an increase in electrical signal results in a decrease in output pressure is obtained by reversing the input signal leads and re-zeroing the instrument.

Modified form of the invention When it is desired to operate a pneumatic actuator directly from the transducer it is necessary to use a relay. Such relay arrangement is shown in FIGURE 7 of the drawing where only a fragment of the casing at the pneumatic end is illustrated.

The relay attaches to the transducer in place of the manifold and since the construction is otherwise similar to that above described like parts have been given the same number.

Thus, FIGURE 7 shows a relay member generally designated 70 detachably connected to the nipple 55 on the connector 53.

Relays of this type are well known on the open market and hence are not more fully described herein. Pressure fluid is delivered through input line 81 and dischargesv from the relay through output line 82. The relay oper ates in response to variations developed by the actuating; chamber 83 which communicates through passage 57,, flame arrestor chamber 52, communicating inlet 5 -1 with,

the chamber 50 as in the case above described for the manifold arrangement.

The operation is similar to that above described except that the output pressure is now a function of the operation of the relay which in turn is actuated responsive to the changes in pressure produced in its actuating chamber 83 which communicates with the chamber 50 of the transducer.

It will be understood that the invention is not to be limited to the specific construction or arrangement of parts shown but that they may be widely modified within the invention defined by the claims.

What is claimed is:

1. In an electro-pneumatic transducer comprising, a casing, a chamber for pressure fluid in said casing, means for delivering pressure fluid to said chamber, an adjustable orifice for bleeding pressure fluid from said chamber including, a nozzle, an orifice in said nozzle, a ball in said orifice, and a beam pivotably mounted to coact with said ball, the combination with said beam of a magnetic means including, an upper pole piece having an opening, a lower pole piece, and a magnet disposed between said upper pole piece and said lower pole piece, said lower pole piece having an upwardly extending cylinder disposed to fit into the opening in said upper pole piece and to form an annular gap therewith, a coil bobbin having a coil mounted thereon disposed to fit in said annular gap, means for delivering an electrical signal to said coil from any suitable source for actuating said coil to move relative said magnetic means, and means connecting said beam to said coil bobbin whereby said beam will move on movement of the coil bobbin, and means on said mag netic means for calibrating the transducer to provide for full input signal range.

2. In an electro-pneumatic transducer as claimed in claim 1 wherein said last mentioned means includes a bore in said magnetic means, a core disposed to be threaded into and out of said bore to adjust the desired gap flux density, and means for locking said core in adjusting position.

3. Electro-magnetic means for an electro-pneumatic transducer including, an upper pole piece having an opening, a lower pole piece having a cylindrical section disposed to fit into said opening and to form an annular gap therewith, a flange arrangement at the lower end of said cylindrical section of the lower pole piece, a magnet connected between the flange and the upper pole piece and disposed to hold the cylindrical section in position in said opening, a coil means disposed in said annular gap, and means for delivering an electrical signal to coil means from any desired source.

4. Electro-magnetic means for an electro-pneumatic transducer including, an upper pole piece having an openin, a lower pole piece having a cylindrical section disposed to fit into said opening and to form an annular gap therewith, a flange arrangement at the lower end of said cylindrical section of the lower pole piece, a magnet connected between the flange and the upper pole piece and disposed to hold the cylindrical section in position in said opening, coil means disposed in said annular gap, and means for delivering an electrical signal to said coil means from any desired source, and means for adjusting the gap flux density for said electro-magnetic means is provided therein.

5. In an electro-magnetic means as claimed in claim 4 wherein means for adjusting the gap flux density includes a bore in said lower pole piece, a span adjuster adapted to be threaded into and out of said bore for providing the desired gap flux density, and means for locking said span adjuster in adjustedposition.

References Cited in thefile of this patent UNITED STATES PATENTS 2,314,860 Lenin Mar. 23, 1943 2,852,948 Renick Sept. 23, 1958 2,915,045 Mackenzie Dec. 1, 1959 FOREIGN PATENTS 859,120 France May 27, 1940 743,847 Germany Jan. 4, 1944 515,358 Belgium Nov. 29, 1952 

